Development of Reduced Peptide Bond Pseudopeptide Michael Acceptors for the Treatment of Human African Trypanosomiasis

Abstract

Human African Trypanosomiasis (HAT) is an endemic protozoan disease widespread in the sub-Saharan region that is caused by T. b. gambiense and T. b. rhodesiense. The development of molecules targeting rhodesain, the main cysteine protease of T. b. rhodesiense, has led to a panel of inhibitors endowed with micro/sub-micromolar activity towards the protozoa. However, whilst impressive binding affinity against rhodesain has been observed, the limited selectivity towards the target still remains a hard challenge for the development of antitrypanosomal agents. In this paper, we report the synthesis, biological evaluation, as well as docking studies of a series of reduced peptide bond pseudopeptide Michael acceptors (SPR10–SPR19) as potential anti-HAT agents. The new molecules show Ki values in the low-micro/sub-micromolar range against rhodesain, coupled with k2nd values between 1314 and 6950 M−1 min−1. With a few exceptions, an appreciable selectivity over human cathepsin L was observed. In in vitro assays against T. b. brucei cultures, SPR16 and SPR18 exhibited single-digit micromolar activity against the protozoa, comparable to those reported for very potent rhodesain inhibitors, while no significant cytotoxicity up to 70 µM towards mammalian cells was observed. The discrepancy between rhodesain inhibition and the antitrypanosomal effect could suggest additional mechanisms of action. The biological characterization of peptide inhibitor SPR34 highlights the essential role played by the reduced bond for the antitrypanosomal effect. Overall, this series of molecules could represent the starting point for further investigations of reduced peptide bond-containing analogs as potential anti-HAT agents

Structure-based lead optimization of peptide-based vinyl methyl ketones as SARS-CoV-2 main protease inhibitors

“…11a was purchased from BIOMOL GmbH (Hamburg, Germany). Inhibitory activity was determined using either a FRET-substrate (SARS-CoV-2 M pro ) [ 26 ] or fluorogenic AMC-substrates (NS2B/NS3 [ 65 ], PL pro [ 64 ], hCatL [ 66 ], and hCatB [ 67 ]). Assays were performed in white flat-bottom 96-well microtiter plates (Greiner bio-one, Kremsmünster, Austria) on a TECAN Infinite F2000 PRO plate reader (Agilent Technologies, Santa Clara, USA) for SARS-CoV-2 M pro or a TECAN Spark 10M (Agilent Technologies) for assays using AMC-substrates.…”

Identification of Dual Inhibitors Targeting Main Protease (Mpro) and Cathepsin L as Potential Anti-SARS-CoV-2 Agents

“…Inhibitory activities were determined as we recently reported. 34 Different from the evaluation toward SARS-CoV-2 M pro , all the analogues showed potent inhibitory properties, with a percentage of residual enzyme activity ranging from 45.1% to 3.4% at the screening concentration (1 μM). Since the aim of this SAR study was the identification of dual inhibitors, only the seven inhibitors of SARS-CoV-2 M pro were biologically characterized against hCatL.…”

“…All the new compounds were then tested against hCatL. Inhibitory activities were determined as we recently reported . Different from the evaluation toward SARS-CoV-2 M pro , all the analogues showed potent inhibitory properties, with a percentage of residual enzyme activity ranging from 45.1% to 3.4% at the screening concentration (1 μM).…”

Trifluoromethylcinnamanilide Michael Acceptors for Treatment of Resistant Bacterial Infections

“…Due to their structure (overall electronic parameters, electron-withdrawing substituents, and conjugated –C(=O)–N(H)– bond), ring-substituted cinnamanilides are able to interact with a variety of biological targets in many signaling pathways in cells, as reported recently [ 12 , 13 , 30 , 63 , 64 , 65 ], and thus meet the requirement of being therapeutically useful multi-target agents. The theory of the dependence of activity on the ability of compounds to act as Michael acceptors would be clearly confirmed by the preparation and biological evaluation of hydrogenated analogues of active cinnamanilides.…”